Protection device, protection method using the same, method for processing signal using the same, and method for detecting quantity of electricity using the same

ABSTRACT

A protection device detects a temperature in a predetermined monitoring place in an electronic apparatus  3  to protect the electronic apparatus  3 , and includes an oscillating circuit  20  for generating a clock signal Vck having a predetermined cycle and a predetermined ON time, and a temperature detection circuit  16  for detecting the temperature in the monitoring place during the ON time of the clock signal Vck. The protection device shuts off supply of electric power to the electronic apparatus  3 , when the temperature in the monitoring place exceeds a predetermined temperature.

TECHNICAL FIELD

The present invention relates to a protection device, a protectionmethod using the same, a method for processing a signal using the same,and a method for detecting a quantity of electricity using the same, theprotection device detecting an abnormal temperature, an abnormalcurrent, or the like of an electronic apparatus to protect theelectronic apparatus by shutting off supply of electric power to theelectronic apparatus.

BACKGROUND ART

In recent years, an electronic apparatus typified by a mobile phoneoperates using electric power supplied from an external power sourcesuch as a battery or an AC (alternating current) adapter. Upon detectingan abnormal state in the electronic apparatus, a protection device ofsuch an electronic apparatus generally shuts off supply of electricpower from the external power source.

Such conventional protection device is disclosed in Patent Document 1,for example. FIG. 12 generally shows a protection device disclosed inPatent Document 1. The protection device according to Patent Document 1uses a lithium-ion battery 80 as an external power source and includesan NMOS (n-type metal-oxide-semiconductor) transistor 81 for controllinga discharging current of the lithium-ion battery 80 and an NMOStransistor 82 for controlling a charging current of the lithium-ionbattery 80.

In order to control the discharging current from the lithium-ion battery80, a control circuit 83 outputs a signal V1 for controlling the NMOStransistor 81. In order to control the charging current to thelithium-ion battery 80, the control circuit 83 outputs a signal V2 forcontrolling the NMOS transistor 82. A temperature detection circuit 84detects an ambient temperature of the NMOS transistor 81, and atemperature detection circuit 85 detects an ambient temperature of theNMOS transistor 82. The temperature detection circuits 84 and 85 output“H (high)” level signals, when the detected temperature is higher thanor equal to a predetermined value, for example, 100° C.

When an output from the temperature detection circuit 84 is at a “L(low)” level, an NMOS transistor 86 connected between the gate and thesource of the NMOS transistor 81 is in the OFF state, allowing thesignal V1 to be applied to the gate of the NMOS transistor 81.Meanwhile, when the output from the temperature detection circuit 84 isat a “H” level, the NMOS transistor 86 is in the ON state, grounding thegate of the NMOS transistor 81 to turn OFF the NMOS transistor 81. Thatis, the ambient temperature of the NMOS transistor 81 exceeding apredetermined value is determined to be an abnormal state, and thus thedischarging current from the lithium-ion battery 80 is shut off.

When an output from the temperature detection circuit 85 is at a “L”level, an NMOS transistor 87 connected between the gate and the sourceof the NMOS transistor 82 is in the OFF state, allowing the signal V2 tobe applied to the gate of the NMOS transistor 82. Meanwhile, when theoutput from the temperature detection circuit 85 is at a “H” level, theNMOS transistor 87 is in the ON state, grounding the gate of the NMOStransistor 82 to turn OFF the NMOS transistor 82. That is, the ambienttemperature of the NMOS transistor 82 exceeding a predetermined value isdetermined to be an abnormal state, and thus the charging current to thelithium-ion battery 80 is shut off.

While the NMOS transistor 81 and the NMOS transistor 82 are in the ONstate, a voltage of the lithium-ion battery 80 is supplied via powersource terminals 88 and 89 to the electronic apparatus.

[Patent Document 1] Japanese Laid-Open Patent Publication No. 11-289656DISCLOSURE OF INVENTION Problems to be Solved by the Invention

However, the above-mentioned conventional protection device detects onlyan ambient temperature of a switching element which turns ON/OFF powersource supply. As an electronic apparatus of recent years typified by amobile phone has been multifunctionalized and increased in electricpower consumption, the number of places where a temperature, a current,or a voltage has to be monitored has been increased. Therefore, there isa problem that electric power consumption increases for detectingtemperatures and quantities of electricity in a plurality of places.

An object of the present invention is to realize a protection device inwhich the above-mentioned conventional problem is solved and theelectric power consumption can be reduced even if a plurality oftemperature detection circuits or circuits for detecting a quantity ofelectricity are provided.

Means for Solving the Problems

To achieve the above-mentioned object, a protection device of thepresent invention is configured to perform detection operation insynchronism with a clock signal which is repeatedly turned ON/OFF in apredetermined cycle.

Specifically, a first protection device according to the presentinvention is directed to a protection device for detecting atemperature, a voltage, or a current in a predetermined monitoring placein an electronic apparatus supplied with electric power from an externalpower source to protect the electronic apparatus from an excessivetemperature, an overvoltage, or an overcurrent, the protection devicecomprising: a detection element arranged in the monitoring place fordetecting the temperature, the voltage, or the current of the electronicapparatus to output an electric signal; an oscillating circuit forgenerating a clock signal having a predetermined cycle and apredetermined ON time; and a detection circuit for detecting theelectric signal during the ON time of the clock signal, the electricsignal being generated in the detection element, wherein supply of theelectric power to the electronic apparatus is shut off according to anoutput signal output from the detection circuit.

According to the first protection device, since the detection operationis performed only during the ON time within a predetermined cyclesynchronous with the clock signal, it is possible to reduce electricpower consumption compared to the conventional protection device inwhich the detection operation is continuously performed. Therefore, evenif the detection operation is performed in a plurality of monitoringplaces in the electronic apparatus, it is possible to suppress theincrease in electric power consumption.

It is preferable that the first protection device further includes aswitching circuit for controlling the supply of the electric power tothe electronic apparatus, the switching circuit being provided for anelectric power supply line between the external power source and theelectronic apparatus, wherein the detection element is a temperaturedetection element for detecting a temperature of the switching circuitto output the electric signal according to the detected temperature, andthe switching circuit is turned off according to the output signal ofthe detection circuit.

Moreover, it is preferable that the first protection device furtherincludes a switching circuit for controlling the supply of the electricpower to the electronic apparatus, the switching circuit being providedfor an electric power supply line between the external power source andthe electronic apparatus, wherein the detection element is a temperaturedetection element for detecting a temperature of an element constitutingthe electronic apparatus to output the electric signal according to thedetected temperature, and the switching circuit is turned off accordingto the output signal of the detection circuit.

Moreover, it is preferable that the first protection device includes aswitching circuit for controlling the supply of the electric power tothe electronic apparatus, the switching circuit being provided for anelectric power supply line between the external power source and theelectronic apparatus, wherein the detection element is a voltagedetection element which is connected to the electric power supply linefor detecting a voltage of the electric power supply line to output theelectric signal according to the detected voltage, and the switchingcircuit is turned off according to the output signal of the detectioncircuit.

Moreover, it is preferable that the first protection device furtherincludes a switching circuit for controlling the supply of the electricpower to the electronic apparatus, the switching circuit being providedfor an electric power supply line between the external power source andthe electronic apparatus, wherein the detection element is a currentdetection element which is connected to the electric power supply linefor detecting a current responsive to an output current of the externalpower source to output the electric signal according to the detectedcurrent, and the switching circuit is turned off according to the outputsignal of the detection circuit.

It is preferable that the first protection device further includes aprotection control circuit for generating the electric signal during theON time of the clock signal, the electric signal being input to thedetection element, wherein the detection element includes detectionelements arranged in N (N is an integer greater than or equal to 2)detection places, and the protection control circuit drives thedetection elements according to N different phases synchronous with theclock signal.

In this case, it is preferable that the protection control circuitincludes a divider circuit for dividing the clock signal by at least N.With this configuration, since the detection operation can besequentially performed in N places according to N cycles obtained bydividing the clock signal by N, the detection operation can be certainlyperformed in a plurality of places while reducing the electric powerconsumption.

It is preferable that the first protection device further includes ajudging circuit which includes a comparison circuit for comparing theoutput signal of the detection circuit with a reference signal servingas a reference and outputting a result of the comparison, wherein thejudging circuit counts an output signal of the comparison circuit, andwhen a result of the count exceeds a predetermined number of times, thejudging circuit shuts off the supply of the electric power to theelectronic apparatus.

With this configuration, it is possible to protect improper operation ofthe protection device caused by extraneous noise or the like.

In this case, it is preferable that the judging circuit furtherincludes: a delay circuit for outputting a signal obtained by delayingthe clock signal for a predetermined time; the detection circuit forintermittently supplying a current to the detection element according tothe clock signal to output a signal generated in the detection element;a logical circuit for performing logical AND operation of the outputsignal of the comparison circuit and the signal output from the delaycircuit; and a counter circuit whose reset terminal receives an outputsignal of the logical circuit and whose clock input terminal receivesthe output signal of the comparison circuit for count operation, whereinthe supply of the electric power to the electronic apparatus is shut offaccording to an output signal of the counter circuit.

It is preferable that the first protection device further includesrecording means for recording a current, a voltage, or a current atwhich the supply of the electric power to the electronic apparatus isshut off.

With this configuration, it is possible to analyze in which operationalenvironment the electronic apparatus has been used.

In this case, it is preferable that the recording means records a biggerone of data detected by the detection circuit and data in the recordingmeans.

Moreover, it is preferable that the first protection device furtherincludes a central processing unit, wherein the recording means operatesaccording to a signal given from the central processing unit.

With this configuration, data for a period when abnormality has beenoccurred is easily collected.

In this case, it is preferable that transmission means for externallytransmitting an internal signal held in the central processing unit isfurther provided.

Moreover, in this case, it is preferable that the central processingunit is connected to a first power source which is detachably provided,and the recording means is connected to a second power source which isprovided independently of the first power source.

A second protection device according to the present invention isdirected to a protection device for detecting temperatures, voltages, orcurrents in predetermined monitoring places in a first electronicapparatus and a second electronic apparatus to protect the electronicapparatuses from an excessive temperature, an overvoltage, or anovercurrent, the protection device including: an oscillating circuit forgenerating a clock signal having a predetermined cycle and apredetermined ON time; a detection circuit for detecting thetemperatures, the voltages, or the currents in the predeterminedmonitoring places during the ON time of the clock signal; and aswitching circuit for shutting off supply of electric power to theelectronic apparatuses according to an output signal of the detectioncircuit; wherein the oscillating circuit and the detection circuit areintegrated to constitute an integrated circuit, the integrated circuitand the first electronic apparatus are mounted on a first substrate, thesecond electronic apparatus is mounted on a second substrate, the firstsubstrate is supplied with the electric power from an external powersource for the first substrate, and the second substrate is suppliedwith the electric power from an external power source for the secondsubstrate, and at least one of the integrated circuit, the firstelectronic apparatus, the second electronic apparatus, the externalpower source for the first substrate, and the external power source forthe second substrate is one of the monitoring places.

According to the second protection device, even if the protection deviceexcepting the detection element, for example, a thermistor, is downsized(formed on one chip) through integration and the electronic apparatusesare mounted on the plurality of substrates, it is possible to certainlydetect temperatures in the plurality of monitoring places of theelectronic apparatuses.

A protection method using a protection device according to the presentinvention is directed to a protection method using a protection devicefor detecting a temperature, a voltage, or a current in a predeterminedmonitoring place in an electronic apparatus to protect the electronicapparatus from an excessive temperature, an overvoltage, or anovercurrent, the protection device including: a detection elementarranged in the monitoring place for detecting a value of thetemperature, the voltage, or the current in the monitoring place; aclock generation circuit for generating a clock signal which is outputfrom the clock generation circuit, the clock signal having apredetermined cycle and a predetermined ON time; and a current sourcefor outputting a signal current during the ON time of the clock signal,the protection method comprising the steps of: collecting a quantity ofelectricity generated by applying the signal current to the detectionelement; and protecting the electronic apparatus according to thecollected quantity of the electricity.

According to the protection method using the protection device of thepresent invention, since the detection operation is performedintermittently, that is, only during the ON time within a predeterminedcycle synchronous with the clock signal, it is possible to reduce theelectric power consumption compared to the conventional protectiondevice in which the detection operation is continuously performed.Therefore, even if the detection operation is performed in a pluralityof monitoring places in the electronic apparatus, it is possible tosuppress the increase in electric power consumption.

A method for processing a signal using a protection device according tothe present invention is directed to a method for processing a signalusing a protection device for detecting a temperature, a voltage, or acurrent in a predetermined monitoring place in an electronic apparatusto protect the electronic apparatus from an excessive temperature, anovervoltage, or an overcurrent, the method comprising the steps of:generating a clock signal having a predetermined cycle and apredetermined ON time; detecting the temperature, the voltage, or thecurrent in the monitoring place during the ON time of the clock signal;shutting off supply of electric power to the electronic apparatusaccording to an output signal of a detection circuit; and recordingoutput data from temperature detection means, voltage detection means,or current detection means at a time when the supply of the electricpower is shut off according to the output signal of the detectioncircuit.

According to the method for processing a signal by the protection deviceof the present invention, even if the detection operation is performedin a plurality of monitoring places in the electronic apparatus, it ispossible to suppress the increase in electric power consumption.Moreover, it is possible to analyze in which operational environment theelectronic apparatus has been used.

It is preferable that the method for processing the signal using theprotection device according to the present invention further includesthe step of transferring the output data to a central processing unitprovided outside.

A method for detecting a quantity of electricity using a protectiondevice according to the present invention is directed to a method fordetecting a quantity of electricity using a protection device fordetecting a temperature, a voltage, or a current in a predeterminedmonitoring place in an electronic apparatus to protect the electronicapparatus from an excessive temperature, an overvoltage, or anovercurrent, the protection device including: a detection elementarranged in the monitoring place for detecting a value of thetemperature, the voltage, or the current in the monitoring place; aclock generation circuit for generating a clock signal which is outputfrom the clock generation circuit, the clock signal having apredetermined cycle and a predetermined ON time; and a current sourcefor outputting a signal current during the ON time of the clock signal,the method comprising the steps of: (a) applying the signal current tothe detection element; and (b) detecting the quantity of the electricitygenerated from the detection element due to the application of thesignal current.

According to the method for detecting the quantity of electricity usingthe protection device of the present invention, even if the detectionoperation is performed in a plurality of monitoring places in theelectronic apparatus, it is possible to suppress the increase in theelectric power consumption.

In the method for detecting the quantity of the electricity using theprotection device according to the present invention, it is preferablethat the monitoring place includes a plurality of monitoring placesprovided in the electronic apparatus, the detection element includes aplurality of detection elements respectively arranged in the pluralityof monitoring places, step (a) includes sequentially applying the signalcurrent from the current source to the plurality of the detectionelements; and step (b) includes sequentially detecting the quantity ofthe electricity generated from each of the detection elements due to thesequential application of the signal current.

EFFECTS OF THE INVENTION

According to the protection device and the method for driving the sameof the present invention, since the detection operation is performed insynchronism with the clock signal, electric power required for detectingabnormality, that is, the electric power consumption can be reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a circuit diagram illustrating a protection device accordingto Embodiment 1 of the present invention.

FIG. 2A is a circuit diagram illustrating a protection device accordingto Embodiment 2 of the present invention.

FIG. 2B is a timing chart illustrating a clock signal Vck and controlsignals Vg1 through Vg4 for driving the protection device according toEmbodiment 2 of the present invention.

FIG. 3 is a perspective view illustrating a mounting example of theprotection device according to Embodiment 2 of the present invention.

FIG. 4 is a circuit diagram illustrating a protection device accordingto Embodiment 3 of the present invention.

FIG. 5 is a circuit diagram illustrating a protection device accordingto Embodiment 4 of the present invention.

FIG. 6 is a circuit diagram illustrating a protection device accordingto Embodiment 5 of the present invention.

FIG. 7 is a circuit diagram illustrating a protection device accordingto Variation 1 of Embodiment 5 of the present invention.

FIG. 8 is a perspective view illustrating a mounting example of theprotection device according to Embodiment 5 of the present invention.

FIG. 9 is a circuit diagram illustrating a protection device accordingto Embodiment 6 of the present invention.

FIG. 10 is a block diagram illustrating a protection device according toEmbodiment 7 of the present invention.

FIG. 11A is an example of a graph illustrating current detection dataoutput from the protection device according to Embodiment 7 of thepresent invention.

FIG. 11B is an example of a graph illustrating a temperature detectiondata output from the protection device according to Embodiment 7 of thepresent invention.

FIG. 12 is a circuit diagram illustrating a conventional protectiondevice.

DESCRIPTION OF REFERENCE NUMERALS

-   -   1 first power source terminal    -   2 second power source terminal    -   3 electronic apparatus    -   3 a electronic apparatus    -   3 b electronic apparatus    -   3 c electronic apparatus    -   4 external power source    -   5 charging device    -   10 battery    -   10A first battery    -   10B second battery    -   10C third battery    -   11 first NMOS transistor    -   12 second NMOS transistor    -   13 control circuit    -   14 first temperature detection circuit    -   140 first thermistor    -   141 fifth NMOS transistor    -   142 first drive resistor    -   15 first comparison circuit    -   150 first comparator    -   151 first reference voltage source    -   152 constant current source    -   16 second temperature detection circuit    -   160 second thermistor    -   161 sixth NMOS transistor    -   162 second drive resistor    -   17 second comparison circuit    -   170 second comparator    -   171 second reference voltage source    -   172 constant current source    -   18 third NMOS transistor    -   19 fourth NMOS transistor    -   20 oscillating circuit    -   21 first PMOS transistor    -   21 a third PMOS transistor    -   22 control circuit    -   22 a second control circuit    -   23 temperature detection circuit    -   23A detection circuit    -   231 first thermistor    -   232 second thermistor    -   233 third thermistor    -   234 fourth thermistor    -   234 a fifth thermistor    -   234 b sixth thermistor    -   235 first NMOS transistor    -   236 second NMOS transistor    -   237 third NMOS transistor    -   238 fourth NMOS transistor    -   239 first detection resistor    -   24 comparison circuit    -   24A comparison circuit    -   24B comparison circuit    -   240 first NMOS transistor    -   241 third PMOS transistor    -   242 fourth PMOS transistor    -   243 first resistor    -   244 first comparator    -   245 reference voltage source    -   246 NOR circuit    -   247 second detection resistor    -   248 second NMOS transistor    -   249 Zener diode    -   25 second PMOS transistor    -   25 a fourth PMOS transistor    -   251 fifth PMOS transistor    -   252 sixth PMOS transistor    -   253 second resistor    -   254 second comparator    -   26 oscillating circuit    -   27 divider circuit (protection control circuit)    -   28 judging circuit    -   28 a first comparison circuit    -   280 comparator    -   281 reference voltage source    -   282 constant current source    -   283 delay circuit    -   284 inverter    -   285 AND circuit    -   286 counter circuit    -   287 NOR circuit    -   29 current detection circuit (circuit for detecting a quantity        of electricity)    -   31 AD converter    -   31 a AD converter    -   31A AD converter    -   32 register    -   32 a register    -   33 CPU    -   34 interface device    -   35 personal computer    -   10A protection device (integrated circuit)    -   101B protection device (integrated circuit)    -   101C protection device (integrated circuit)    -   101D protection device (integrated circuit)    -   102 wiring    -   102A wiring    -   102B wiring pattern    -   121 first IC chip    -   122 second IC chip    -   123 third IC chip    -   124 fourth IC chip    -   125 fifth IC chip    -   300 mounting substrate    -   301 first mounting substrate    -   302 second mounting substrate    -   303 third mounting substrate    -   400 integrated circuit (protection device)    -   401 voltage detection protection circuit    -   402 current detection protection circuit    -   403 temperature detection protection circuit    -   404 protection control circuit    -   405 analog output circuit    -   410 thermistor    -   420 external power source    -   430 battery    -   440 charging device    -   450 first switch    -   460 second switch    -   470 resistor    -   480 external device    -   481 AD converter    -   482 CPU

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

Embodiment 1 according to the present invention will be described withreference to the drawings.

FIG. 1 shows a circuit configuration of a protection device according toEmbodiment 1 of the present invention. As shown in FIG. 1, theprotection device according to Embodiment 1 performs protectionoperation for an electronic apparatus 3 which has a first power sourceterminal 1 and a second power source terminal 2, wherein the first powersource terminal 1 is connected to a positive electrode of a battery 10serving as an external power source, and the second power sourceterminal 2 is connected to a grounded negative electrode of the battery10 via a first NMOS transistor 11 and a second NMOS transistor.

The first NMOS transistor 11 controls a discharging current of thebattery 10, and the second NMOS transistor 12 controls a chargingcurrent of the battery 10. The gate of the first NMOS transistor 11receives a first signal V1 for controlling the first NMOS transistor 11from a control circuit 13 connected to the positive electrode of thebattery 10. The gate of the second NMOS transistor 12 receives a secondsignal V2 for controlling the second NMOS transistor 12 from the controlcircuit 13.

The protection device includes: a third NMOS transistor 18 connectedbetween the gate and the source of the first NMOS transistor 11; a firsttemperature detection circuit 14 having a first thermistor 140; a firstcomparison circuit 15 for feeding a constant current to the firsttemperature detection circuit 14 and comparing a voltage drop across thefirst thermistor 140 with a reference voltage to turn ON/OFF the thirdNMOS transistor 18 depending on a result of the comparison; a fourthNMOS transistor 19 connected between the gate and the source of thesecond NMOS transistor 12; a second temperature detection circuit 16having a second thermistor 160; a second comparison circuit 17 forfeeding a constant current to the second temperature detection circuit16 and comparing a voltage drop across the second thermistor 160 with areference voltage to turn ON/OFF the fourth NMOS transistor 19 dependingon a result of the comparison; and an oscillating circuit 20 forgenerating a clock signal Vck which is output to the first temperaturedetection circuit 14 and the second temperature detection circuit 16,wherein the clock signal Vck repeatedly changes between high and lowlevels in a cycle Ts. Here, a period when the clock signal Vck is at a“H” level is understood to be an ON time Ton.

Specifically, the first temperature detection circuit 14 includes thefirst thermistor 140 one terminal of which is grounded, and a fifth NMOStransistor 141. The fifth NMOS transistor 141 has the source connectedto the other terminal of the first thermistor 140, the gate forreceiving the clock signal Vck via a first drive resistor 142, and thedrain for receiving the constant current from the first comparisoncircuit 15. To detect an ambient temperature of the first NMOStransistor 11, the first thermistor 140 is arranged near the first NMOStransistor 11 and fed with a current via the fifth NMOS transistor 141.

The first comparison circuit 15 includes a first comparator 150 whichhas a positive phase terminal for receiving the reference voltage from afirst reference voltage source 151 and a negative phase terminalconnected to a first constant current source 152. The first constantcurrent source 152 feeds the constant current to the first thermistor140 via the fifth NMOS transistor 141 in the first temperature detectioncircuit 14 and compares the voltage drop across the first thermistor 140with the reference voltage of the first reference voltage source 151.

Likewise, the second temperature detection circuit 16 includes a sixthNMOS transistor 161 and the second thermistor 160 one terminal of whichis grounded. The sixth NMOS transistor 161 has the source connected tothe other terminal of the second thermistor 160, the gate for receivingthe clock signal Vck via a second drive resistor 162, and the drain forreceiving the constant current from the second comparison circuit 17. Todetect an ambient temperature of the second NMOS transistor 12, thesecond thermistor 160 is arranged near the second NMOS transistor 12 andfed with a current via the sixth NMOS transistor 161.

The second comparison circuit 17 includes a second comparator 170 whichhas a positive phase terminal for receiving the reference voltage from asecond reference voltage source 171 and a negative phase terminalconnected to a second constant current source 172. The second constantcurrent source 172 feeds the constant current to the second thermistor160 via the sixth NMOS transistor 161 in the second temperaturedetection circuit 16 and compares the voltage drop across the secondthermistor 160 with the reference voltage of the second referencevoltage source 171.

Operation of the protection device having the above-mentionedconfiguration according to Embodiment 1 of the present invention will bedescribed below.

First, when the clock signal Vck is at a “L” level, both the fifth NMOStransistor 141 in the first temperature detection circuit 14 and thesixth NMOS transistor 161 in the second temperature detection circuit 16are in the OFF state, and thus the first thermistor 140 and the secondthermistor 160 are not fed with currents. Therefore, since detectioncurrents of the first comparison circuit 15 and the second comparisoncircuit 17 are 0, the first comparison circuit 15 and the secondcomparison circuit 17 output “L” level signals respectively to the gatesof the third NMOS transistor 18 and the fourth NMOS transistor 19. Thisturns OFF both the third NMOS transistor 18 and the fourth NMOStransistor 19, so that the signal V1 from the control circuit 13 isapplied to the gate of the first NMOS transistor 11, and the signal V2from the control circuit 13 is applied to the gate of the second NMOStransistor 12.

Next, when the clock signal Vck is at the “H” level, both the fifth NMOStransistor 141 in the first temperature detection circuit 14 and thesixth NMOS transistor 161 of the second temperature detection circuit 16are in the ON state, and thus the first thermistor 140 and the secondthermistor 160 are fed with the currents. It is provided that the firstthermistor 140 and the second thermistor 160 have such a characteristicthat resistance values of the first thermistor 140 and the secondthermistor 160 decrease as the temperature increases (negativeresistance temperature coefficient). In this case, the voltage dropsacross the first thermistor 140 and the second thermistor 160 decreaseas the temperature increases. That is, when the clock signal Vck is atthe “H” level, detection voltages of the first comparison circuit 15 andthe second comparison circuit 17 decrease as the temperature increases.

The first comparison circuit 15 compares the detection voltage with thereference voltage (for example, the amount of a voltage drop which isdetermined by a resistance value for the temperature of the firstthermistor 140 corresponding to 100° C.) of the first reference voltagesource 151. Then, the first comparison circuit 15 outputs a result ofthe comparison to the gate of the third NMOS transistor 18. The sameholds for the second comparison circuit 17. When an output signal fromthe first comparison circuit 15 is at the “L” level, the third NMOStransistor 18 is in the OFF state, and thus the signal V1 is appliedfrom the control circuit 13 to the gate of the first NMOS transistor 11.Compared to this, when the output signal from the first comparisoncircuit 15 is at the “H” level, the third NMOS transistor 18 is in theON state, and thus the first NMOS transistor 11 is in the OFF state.That is, the protection device determines that the ambient temperatureof the first NMOS transistor 11 exceeding 100° C., which is apredetermined value, is an abnormal state and shuts off the dischargingcurrent from the battery 10.

Likewise, when an output signal from the second comparison circuit 17 isat the “L” level, the fourth NMOS transistor 19 is in the OFF state, andthus the signal V2 is applied from the control circuit 13 to the gate ofthe second NMOS transistor 12. Compared to this, when the output signalfrom the second comparison circuit 17 is at the “H” level, the fourthNMOS transistor 19 is in the ON state, and thus the second NMOStransistor 12 is in the OFF state. That is, the protection devicedetermines that the ambient temperature of the first NMOS transistor 11exceeding 100° C., which is a predetermined value, is an abnormal stateand shuts off the discharging current from the battery 10.

As described above, according to Embodiment 1, only during the ON timeTon of the clock signal Vck, the first temperature detection circuit 14and the second temperature detection circuit 16 are fed with thecurrents, generating the detection voltages. The detection is notperformed during times other than the ON time. However, even if theelectric power consumption of the transistor abnormally increases forany cause, it takes a certain amount of time until the temperatureincreases to a critical level leading to a breakdown of the transistor.An OFF time in which the clock signal Vck is at the “L” level and the ONtime Ton which is a detection time also depend on transient thermalresistance of the transistor whose temperature is to be detected. TheOFF time can be set to between several milliseconds and several seconds,and several microseconds are sufficient for the ON time Ton. Therefore,compared to the conventional configuration in which a current is fed allthe time, current consumption required for the detection can be reducedto Ton/Ts, that is, less than 1/1000.

Embodiment 2

Embodiment 2 according to the present invention will be described belowwith reference to the drawings.

In Embodiment 1 of FIG. 1, the description has been given of theprotection device in which the first NMOS transistor 11 and the secondNMOS transistor 12 connected to the negative electrode of the battery 10and to a ground line connecting to the power source terminal 2 of theelectronic apparatus 3 respectively shut off the discharging current andthe charging current of the battery 10.

The protection device of the present invention is applicable toembodiments other than Embodiment 1. For example, in a protection deviceaccording to Embodiment 2 shown in FIG. 2A, a battery 10 and anelectronic apparatus 3 share a ground line, and a first PMOS transistor21 serially connected to a power source line shuts off a supply currentfrom the battery 10 to the electronic apparatus 3.

As shown in FIG. 2A, the protection device according to Embodiment 2performs protection operation for the electronic apparatus 3 which has afirst power source terminal 1 and a second power source terminal 2,wherein the first power source terminal 1 is connected to a positiveelectrode of the battery 10 serving as an external power source via thefirst PMOS transistor 21, and the second power source terminal 2 isconnected to a grounded negative electrode of the battery 10.

The first PMOS transistor 21 controls supply of electric power from thebattery 10 to the electronic apparatus 3. The gate of the first PMOStransistor 21 receives a signal V1 for controlling the first PMOStransistor 21 from a control circuit 22 connected to the negativeelectrode of the battery 10.

The protection device includes: a second PMOS transistor 25 connectedbetween the gate and the source of the first PMOS transistor 21; atemperature detection circuit 23 having a first thermistor 231, a secondthermistor 232, a second thermistor 233, and a fourth thermistor 234; acomparison circuit 24 for feeding a constant current to the temperaturedetection circuit 23 and comparing a voltage drop across each of thethermistors 231 through 234 with a reference voltage to turn ON/OFF thesecond PMOS transistor 25 depending on a result of the comparison; anoscillating circuit 26 for generating a clock signal Vck which is outputtherefrom, wherein the clock signal Vck repeatedly changes between highand low levels in a cycle Ts; and a divider circuit 27 serving as aprotection control circuit, wherein the divider circuit 27 divides theclock signal Vek at least by 4 to produce control signals Vg1 throughVg4 which are output to the temperature detection circuit 23. Here, aperiod when the clock signal Vck is at the “H” level is understood to bean ON time Ton. FIG. 2B shows a timing diagram of the clock signal Vckand the control signals Vg1 through Vg4.

Specifically, the temperature detection circuit 23 includes a firstthermistor 231 one terminal of which is grounded, a second thermistor232 one terminal of which is grounded, a third thermistor 233 oneterminal of which is grounded, a fourth thermistor 234 one terminal ofwhich is grounded, a first NMOS transistor 235, a second NMOS transistor236, a third NMOS transistor 237, and a fourth NMOS transistor 238. Thefirst NMOS transistor 235 has the source connected to the other terminalof the first thermistor 231, the gate for receiving the control signalVg1, and the drain for receiving the constant current from thecomparison circuit 24. The second NMOS transistor 236 has the sourceconnected to the other terminal of the second thermistor 232, the gatefor receiving the control signal Vg2, and the drain for receiving theconstant current from the comparison circuit 24. The third NMOStransistor 237 has the source connected to the other terminal of thethird thermistor 233, the gate for receiving the control signal Vg3, andthe drain for receiving the constant current from the comparison circuit24. The fourth NMOS transistor 238 has the source connected to the otherterminal of the fourth thermistor 234, the gate for receiving thecontrol signal Vg4, and the drain for receiving the constant currentfrom the comparison circuit 24. Here, for example, the first thermistor231 is arranged near the first PMOS transistor 11 in order to detect anambient temperature of the first PMOS transistor 21, and the secondthrough fourth thermistors 232-234 are respectively provided inpredetermined monitoring places in the electronic apparatus 3.

In FIG. 3, as an example, an arrangement of the second thermistor 232and the third thermistor 233 and a mounting state of a protection device101A are shown. In this case, the comparison circuit 24, the oscillatingcircuit 26, the divider circuit 27, and NMOS transistors 235 through 238of the temperature detection circuit 23 are integrated (on one chip) inthe protection device 101A. As shown in FIG. 3, a first IC chip 121 anda second IC chip 122 which are to be monitored and the protection device101A are mounted on a mounting substrate 300. The first IC chip 121 andthe second IC chip 122 constitute the electronic apparatus 3. Theprotection device 101A protects the first IC chip 121 and the second ICchip 122 from overheating. For example, the second thermistor 232 isarranged near a side surface of the first IC chip 121, and the thirdthermistor 233 is arranged near a side surface of the second IC chip122. Here, the protection device 101A is electrically connected to thethermistors 232 and 233 via wiring 102. It is to be noted that the firstPMOS transistor 21 can be integrated in the protection device 101A.

Although not shown, the comparison circuit 24 has four components eachof which includes the same comparator 150, reference voltage source 151,and constant current source 152 as those of the first comparison circuit15 of FIG. 1 and outputs a negated logical sum (NOR) of output signalsfrom the comparators. The comparison circuit 24 has a first detectionterminal I1, a second detection terminal I2, a third detection terminalI3, a fourth detection terminal I4, and an output terminal Out. From thefirst detection terminal I1, the constant current is fed to the firstthermistor 231 via the first NMOS transistor 235 in the temperaturedetection circuit 23, and the voltage drop across the first thermistor231 is detected and compared with the reference voltage. Likewise, fromthe second through fourth detection terminals I2-I4, the constantcurrent is fed to the second through fourth thermistors 232-234 via thesecond through fourth NMOS transistors 236-238 respectively, and thevoltage drop across each of the thermistors 232 through 234 is detectedand compared with the reference voltage.

Operation of the protection device having the above-mentionedconfiguration according to Embodiment 2 of the present invention will bedescribed below. First, when the clock signal Vck is at the “L” level,the first through fourth NMOS transistors 235-238 in the temperaturedetection circuit 23 are in the OFF state, and thus the first throughsecond thermistors 231-234 are not fed with a current. Therefore, adetection current of the comparison circuit 24 is 0, and thus a signalat a “H” level is output to the gate of the second PMOS transistor 25.This turns OFF the second PMOS transistor 25, allowing the signal V1from the control circuit 22 to be applied to the gate of the first PMOStransistor 21.

Next, when the clock signal Vck is at the “H” level, one of the controlsignals Vg1 through Vg4 is at a “H” level due to the divider circuit 27.For example, when the control signal Vg1 is at the “H” level, the firstNMOS transistor 235 is in the ON state, and thus the first thermistor231 is fed with the current. It is provided that the first thermistor231 has such a characteristic that the resistance value of the firstthermistor 231 decreases as the temperature increases. In this case, thevoltage drop across the first thermistor 231 decreases as thetemperature increases. That is, when the control signal Vg1 is at the“H” level, a voltage of the first detection terminal I1 of thecomparison circuit 24 decreases as the temperature increases. Thecomparison circuit 24 compares the voltage of the first detectionterminal I1 with the reference voltage (for example, the amount of avoltage drop determined by a resistance value for the temperature of thefirst thermistor 231 corresponding to 100° C.). Then, the comparisoncircuit 24 outputs a result of the comparison from the output terminalOut to the gate of the second PMOS transistor 25. When the outputterminal Out of the comparison circuit 24 is at a “H” level, the secondPMOS transistor 25 is in the OFF state, so that the signal V1 is appliedto the gate of the first PMOS transistor 21 from the control circuit 22.Compared to this, when the output terminal Out of the comparison circuit24 is at a “L” level, the second PMOS transistor 25 is in the ON state,and thus the first PMOS transistor 21 is in the OFF state. That is, theprotection device determines that the ambient temperature of the firstPMOS transistor 21 exceeding 100° C., which is a predetermined value, isan abnormal state and shuts off the supply current from the battery 10to the electronic apparatus 3.

Likewise, when the control signal Vg2 is at the “H” level, the secondNMOS transistor 236 in the temperature detection circuit 23 is in the ONstate, and thus the second thermistor 232 is fed with a current. It isprovided that the second thermistor 232 has such a characteristic thatthe resistance value of the second thermistor 232 decreases as thetemperature increases. In this case, the voltage drop across the secondthermistor 232 decreases as the temperature increases. That is, when thecontrol signal Vg2 is at the “H” level, a voltage of the seconddetection terminal I2 of the comparison circuit 24 decreases as thetemperature increases. The comparison circuit 24 compares the voltage ofthe second detection terminal I2 with the reference voltage (forexample, the amount of a voltage drop determined by a resistance valuefor the temperature of the second thermistor 232 corresponding to 100°C.). Then, the comparison circuit 24 outputs a result of the comparisonfrom the output terminal Out to the gate of the second PMOS transistor25. That is, the protection device determines that the temperature ofthe second thermistor 232 arranged in a predetermined monitoring placein the electronic apparatus 3 exceeding a predetermined value is anabnormal state and shuts off the supply current from the battery 10 tothe electronic apparatus 3.

When the control signal Vg3 or the Vg4 is at the “H” level, the sameoperation as mentioned above is sequentially performed. The protectiondevice determines that the temperature of the third thermistor 233 orthe fourth thermistor 234 arranged in other monitoring place in theelectronic apparatus 3 exceeding a predetermined value is an abnormalsate and shuts off the supply current from the battery 10 to theelectronic apparatus 3.

As described above, according to Embodiment 2, the detection terminalsI1 through I4 for the temperature detection circuit 23 and for thecomparison circuit 24 are fed with the current only during the ON timeTon in which the control signals Vg1 through Vg4 obtained by dividingthe clock signal Vck are respectively at the “H” level. The detection isnot performed during times other than the ON time. However, it takes acertain amount of time until electric power consumption in eachmonitoring place abnormally increases and the temperature increases to acritical level leading to a breakdown. Therefore, compared to the casewhere the detection current is fed all the time, the consumption currentrequired for the detection can be reduced to Ton/(4 Ts). Of course, thenumber of places for monitoring the temperature is not limited to four.Less than or more than four monitoring places are possible.

According to the protection device according to Embodiment 2, aplurality of temperature detection means (thermistors) sequentiallyperform detection operation in a time division manner, so that thedetection current is distributed not to concentrate in a certain time.Therefore, noise occurring in a detection operation state is reduced andimproper operation is prevented. Moreover, specifying a detection placeof an abnormal state is also facilitated.

Embodiment 3

Embodiment 3 according to the present invention will be described belowwith reference to the drawings.

FIG. 4 shows a circuit configuration of a protection device according toEmbodiment 3 of the present invention. In FIG. 4, the same components asthose of FIG. 2 are given the same reference numerals and descriptionsthereof are omitted.

The protection device according to Embodiment 3 is different from theprotection device according to Embodiment 2 in that a judging circuit 28is provided. It is to be noted that, in FIG. 4, detailed configurationsof the electronic apparatus 3 and the temperature detection circuit 23are the same as those of Embodiment 2, and thus descriptions thereof areomitted.

As shown in FIG. 4, an output signal from the temperature detectioncircuit 23 detected during the ON time of a control signal Vg1 of adivider circuit 27 is coupled to a first detection terminal I1 of thejudging circuit 28, and an output signal from the temperature detectioncircuit 23 detected during the ON time of a control signal Vg2 iscoupled to a second detection terminal I2 of the judging circuit 28.Likewise, an output signal from the temperature detection circuit 23detected due to a control signal Vg3 is coupled to a third detectionterminal I3 of the judging circuit 28, and an output signal from thetemperature detection circuit 23 detected due to a control signal Vg iscoupled to a fourth detection terminal I4 of the judging circuit 28.

The judging circuit 28 includes: a first comparison circuit 28 aconnected to the first detection terminal I1; a delay circuit 283 fordelaying the control signal Vg1 for a predetermined time which is outputtherefrom; an AND circuit 285 one input terminal of which receives thedelayed signal from the delay circuit and the other input terminal ofwhich receives an output signal from the comparison circuit 28 a via aninverter 284; a counter circuit 286 having a clock input terminal CLKfor receiving the output signal from the comparison circuit 28 a, and areset terminal R for receiving an output signal from the AND circuit285; and a NOR circuit 287 one input terminal of which is connected toan output terminal Q of the counter circuit 286, and an output terminalOut of which is connected to the gate of the second PMOS transistor 25.

The first comparison circuit 28 a includes a comparator 280 which has apositive phase terminal for receiving a reference voltage from areference voltage source 281 and a negative phase terminal connected toa constant current source 282 and to the first detection terminal I1.The comparator 280 compares a detection voltage which is input from thetemperature detection circuit 23 to the first detection terminal I1 withthe reference voltage from the reference voltage source 281. Meanwhile,the constant current source 282 feeds a predetermined current to thetemperature detection circuit 23 via the first detection terminal I1. Asdescribed above, the comparator 280, the reference voltage source 281,and the constant current source 282 have the same configurations asthose of the comparison circuit of FIG. 1. Although not shown, thesecond through fourth detection terminals I2-I4 are provided with thesame comparison circuits 28 a.

When a “H” level is input to the reset terminal R of the counter circuit286, the counter circuit 286 resets a count number to 0, and counts asignal at a “H” level input to the clock input terminal CLK. When thecount number reaches a predetermined value, an output signal at a “H”level is output from the output terminal Q.

A delay circuit 283, an inverter 284, an AND circuits 285, and the NORcircuit are also provided for each of the control signals Vg2 throughVg4.

Operation of the protection device having the above-mentionedconfiguration according to Embodiment 3 of the present invention will bedescribed below. Here, in synchronization with the respective controlsignals Vg1 through Vg4 obtained by dividing the clock signal Vck,detection signals in respective monitoring places in the electronicapparatus (not shown) are output from the temperature detection circuit23. The output detection signals are output to the first comparisoncircuit 28 a and the other comparison circuits respectively connected tothe first through fourth detection terminals I1-I4, and compared withthe reference voltage in the comparison circuit 28 a and the othercomparison circuits. This configuration is the same as that inEmbodiment 2.

Here, with reference to the control signal Vg1 and the detection signalinput to the first detection terminal I1, operation of the delay circuit283, the inverter 284, the AND circuit 285, the counter circuit 286, andthe NOR circuit 287 will be described.

A delay time of the delay circuit 283 is set to be longer than or equalto a duration from a rise of the control signal Vg1 until the inverter284 outputs an inversion signal of an output signal of the comparator280. Here, a reason why the delay circuit 283 is provided between thedivider circuit 27 and a terminal of the AND circuit 285 for receivingthe control signal Vg1 is as follows. If the delay circuit 283 were notprovided in the case where the comparator 280 detects abnormality fromthe detection signal input to the first detection terminal I1 andchanges its output signal from a “L” level to a “H” level, an output ofthe inverter 284 would become “H” level at the rise of the controlsignal Vg1, resetting the counter circuit 286 in every cycle. Moreover,the delay circuit 283 transmits the control signal Vg1 with only therise of the control signal Vg1 being delayed but a fall of the controlsignal Vg1 not being delayed. Therefore, the case where the AND circuit285 outputs a “H” level means that the output signal of the comparator280 becomes the “L” level within the ON time of the control signal Vg1.This is normal operation in which no abnormality is detected.

Next, once the comparator 280 detects abnormality from the detectionsignal input to the first detection terminal I1 and changes its outputsignal from the “L” level to the “H” level, the rise of the outputsignal of the delay circuit 283 is ignored in the AND circuit 285. Thecounter circuit 286 counts the output signal at the “H” level of thecomparator 280. If this abnormality detection is any improper operation,the output signal from the comparator 280 eventually becomes “L” level.As a result, an output signal from the AND circuit 285 becomes “H” levelat the rise of the output signal from the delay circuit 283, whichresets a count value of the counter circuit 286. However, if theabnormal state lasts, the counter circuit 286 continues counting up, andwhen the count value reaches a predetermined value, the counter circuit286 outputs the “H” level to the output terminal Q. That is, if anabnormality detection signal output in synchronization with the controlsignal Vg1 is repeatedly generated for a predetermined number of times,the counter circuit 286 outputs the “H” level. Therefore, an output ofthe NOR circuit 287 becomes “L” level, so that the second PMOStransistor 25 is turned ON. Therefore, the first PMOS transistor 21 isshort-circuited between the gate and the source, so that the first PMOStransistor 21 is turned OFF. As a result, the supply current from thebattery 10 to the electronic apparatus is shut off. It is to be notedthat the same operation holds for the abnormality detection in the othermonitoring places.

As described above, according to Embodiment 3, an abnormal state isrecognized and the protection operation is performed only when theabnormality detection signal is repeatedly generated for a predeterminednumber of times, so that it is possible to prevent the improperoperation of the protection device caused by extraneous noise or thelike.

Embodiment 4

Embodiment 4 according to the present invention will be described belowwith reference to the drawings.

FIG. 5 shows a circuit configuration of a protection device according toEmbodiment 4 of the present invention. In FIG. 5, the same components asthose of FIG. 2 are given the same reference numerals and descriptionsthereof are omitted.

As shown in FIG. 5, the protection device according to Embodiment 4 isdifferent from the protection device according to Embodiment 2 in thatthe protection device of Embodiment 4 includes a current detectioncircuit 29 forming a current mirror with the first PMOS transistor 21,and further, a detection circuit 23A includes a first detection resistor239 as an alternative to the first thermistor 231 for temperaturedetection of the first PMOS transistor 21, wherein an output current ofthe current detection circuit 29 is fed to the first detection resistor239 via a first NMOS transistor 240 so that the amount of a voltage dropacross the first detection resistor 239 is detected at a first detectionterminal I5 of a comparison circuit 24A. Another difference is that asan alternative to the second thermistor 232 for temperature detection, asecond detection resistor 247 is provided, and an output current of aZener diode 249, which is a voltage detection circuit, is fed to thesecond detection resistor 247 via a second NMOS transistor 248 so thatthe amount of a voltage drop across the second detection resistor 247 isdetected at a second detection terminal I6 of the comparison circuit24A.

Operation of the protection device having the above-mentionedconfiguration according to Embodiment 4 of the present invention will bedescribed below. Specifically, descriptions are given of operation withrespect to current detection and operation with respect to voltagedetection which are different from those of Embodiment 2.

First, the operation with respect to the current detection will bedescribed.

The protection device detects a current flowing through the first PMOStransistor 21 by the current detection circuit 29. When the controlsignal Vg1 is at a “H” level, the comparison circuit 24A compares thedetection value of the first detection terminal I5 with the referencevoltage and then outputs a result of the comparison from the outputterminal Out. Although details are not shown, the comparison circuit 24Ais configured such that when the amount of current flowing through thefirst detection resistor 239 increases and the detection value of thefirst detection terminal I5 of the comparison circuit 24A exceeds thereference voltage, the comparison circuit 24A causes the output terminalOut to transition to a “L” level. Therefore, when the output terminalOut of the comparison circuit 24A is at a “H” level, a signal V1 of anormal state is applied to the gate of the first PMOS transistor 21.Meanwhile, when output terminal Out of the comparison circuit 24A is atthe “L” level, the first PMOS transistor 21 is in the OFF state. Thatis, the protection device determines that the current of the first PMOStransistor 21 exceeding a predetermined value is an abnormal state andshuts off supply current from the battery 10 to electronic apparatus 3.

Next, the operation with respect to the voltage detection will bedescribed.

In the protection device according to Embodiment 4, the Zener diode 249and the second detection resistor 247 are serially connected to bothterminals of the battery 10 via the second NMOS transistor 248. It isprovided that the voltage of the battery 10 is denoted by Vb and theZener voltage of the Zener diode 249 is denoted by Vz. In this case,when the second NMOS transistor 248 is in the ON state, a voltage of(Vb-Vz) is generated across the second detection resistor 247, and thegenerated voltage (Vb-Vz) is applied to the second detection terminal I6of the comparison circuit 24A. The comparison circuit 24A is configuredsuch that when the detection value of the second detection terminal I6exceeds the reference voltage as in the case of the first detectionterminal I5, the comparison circuit 24A causes the output terminal Outto transition to the “L” level. Therefore, when the output terminal Outof the comparison circuit 24A is at the “L” level, the first PMOStransistor 21 is in the OFF state. That is, the protection devicedetermines that the voltage Vb of the battery 10 exceeding apredetermined value is a false connection to an irregular battery or anabnormal state such as overcharging and shuts off the supply currentfrom the battery 10 to the electronic apparatus 3.

As described above, the protection device of the present invention isnot limited to temperature detection of the electronic apparatus 3, andis applicable to protection operation through the current detection orthe voltage detection. Moreover, the protection device of the presentinvention can adopt the improper detection preventing function in whichthe protection operation is performed after the abnormal state isrepeatedly detected for a predetermined number of times as in Embodiment3.

Embodiment 5

Embodiment 5 according to the present invention will be described belowwith reference to the drawings.

FIG. 6 shows a circuit configuration of a protection device according toEmbodiment 5 of the present invention. In FIG. 6, the same components asthose of FIG. 2 are given the same reference numerals and descriptionsthereof are omitted.

As shown in FIG. 6, the protection device according to Embodiment 5 isdifferent from the protection device according to Embodiment 2 inconfiguration of a comparison circuit 24B, and in that AD(analog-to-digital) converters 31 and 31 a, registers 32 and 32 a, and acentral processing unit (CPU) 33 are provided. It is to be noted that,in FIG. 6, the electronic apparatus 3 is divided into a first electronicapparatus 3 a and a second electronic apparatus 3 b. Moreover,components identified by a reference number 101B are components whichcan be integrated in the protection device of the present embodiment asan integrated circuit. Although not shown, the CPU 33 is connected to adetachable power source.

The comparison circuit 24B according to Embodiment 5 includes: a thirdPMOS transistor 241 and a fourth PMOS transistor 242 forming a currentmirror; a first resistor 243 one terminal of which is connected to thedrain of the fourth PMOS transistor 242 and the other terminal of whichis grounded; a first comparator 244 having a negative phase terminalconnected to a reference voltage source 245 and a positive phaseterminal connected to the one terminal of the first resistor 243; and aNOR circuit 246 one input terminal of which is connected to an outputterminal of the first comparator 244 and an output terminal Out of whichis connected to the gate of the second PMOS transistor 25. Likewise, thecomparison circuit 24B includes a fifth PMOS transistor 251 and a sixthPMOS transistor 252 forming a current mirror, a second resistor 253connected to the sixth PMOS transistor 252, and a second comparator 254.

The third PMOS transistor 241 feeds a current from a third detectionterminal I3 of the comparison circuit 24B via the third NMOS transistor237 of the temperature detection circuit 23 to the third thermistor 233.At this point, a current output from the fourth PMOS transistor 242flows to the first resistor 243, generating a voltage Vs across thefirst resistor 243, and the voltage Vs serving as a detection value iscompared with a reference voltage of the reference voltage source 245 bythe first comparator 244.

In a manner similar to this, the fifth PMOS transistor 251 feeds acurrent from a fourth detection terminal I4 of the comparison circuit24B via the fourth NMOS transistor 238 of the temperature detectioncircuit 23 to the fourth thermistor 234. At this point, a current outputfrom the sixth PMOS transistor 252 flows to the second resistor 253,generating a voltage Vs across the second resistor 253, and the voltageVs serving as a detection value is compared with the reference voltageof the reference voltage source 245 by the second comparator 253.

Although not shown, the comparison circuit 24B has a configuration inwhich like current mirrors and like comparators form pairs for the otherNMOS transistors and the other thermistors of the temperature detectioncircuit 23. Output signals from the other comparators are respectivelyinput to the other input terminals of the NOR circuit 246.

In Embodiment 5, the AD converters 31 and 31 a receive the detectionvoltages Vs respectively generated across the resistors 243 and 253. Theregisters 32 and 32 a receive output signals respectively from the ADconverters 31 and 31 a, and an output signal from an output terminal Outof the NOR circuit 246. The CPU 33 receives output signals at least fromthe registers 32 and 32 a.

Specifically, the voltage values of the detection voltages Vsrespectively detected by the resistors 243 and 253 are converted todigital data by the AD converters 31 and 31 a and output respectively tothe registers 32 and 32 a. A signal of the output terminal Out of thecomparison circuit 24B is input as a capture signal to each of theregisters 32 and 32 a. The CPU 33 reads the data from the registers 32and 32 a. Although not shown, the other detection voltage values of thecomparison circuit 24B are converted in the same manner to digital databy the AD converter 31, and sent to registers (not shown) and read bythe CPU 33.

Operation of the protection device having the above-mentionedconfiguration according to Embodiment 5 of the present invention will bedescribed below. Here, in synchronization with control signals Vg1through Vg4 obtained by dividing a clock signal Vck, detection signalsin respective monitoring places in the electronic apparatus (not shown)are input from the temperature detection circuit 23 to the comparisoncircuit 24B connected thereto. This configuration is the same as that ofEmbodiment 2.

Here, referring to the control signal Vg3 and a signal of the thirddetection terminal I3, operation of the comparison circuit 24B will bedescribed.

The third PMOS transistor 241 has the gate and the drain short-circuitedto be connected to the drain of the third NMOS transistor 237. It isprovided that a “H” level of the control signal Vg3 input to the gate ofthe third NMOS transistor 237 is a constant voltage. In this case,provided that a resistance value of the third thermistor 233 is R3, thecurrent I fed to the third thermistor 233 is represented by thefollowing expression (1).

I=(Vg3−Vt)/R3  (1)

Here, Vt is the threshold voltage between the gate and the source of thethird NMOS transistor 237. The current I represented by the expression(1) flows through the third PMOS transistor 241, and a current dependingon the mirror ratio also flows to the fourth PMOS transistor 242 formingthe current mirror with the third PMOS transistor 241. For example,provided that the mirror ratio is 1 and the resistance value of thefirst resistor 243 is Rs, the detection voltage Vs is represented by thefollowing expression (2).

Vs=Rs×I=Rs(Vg3−Vt)/R3  (2)

That is, when the resistance value R3 decreases as the temperature ofthe third thermistor 233 increases, the detection voltage Vs increases.The first comparator 244 compares the detection voltage Vs with thereference voltage (for example, the amount of a voltage drop determinedby a resistance value for the temperature of the thermistorcorresponding to 100° C.), and outputs a result of the comparison fromthe output terminal Out. As described above, the comparison circuit 24Bis not limited to the configuration of Embodiment 2 and capable ofsetting of the relationship between the temperature and the detectionvoltage Vs in consideration of characteristics of the thermistor.

Moreover, the detection voltage Vs is converted by the AD converter 31to digital data which is output to the register 32. As described above,the output signal from the output terminal Out of the comparison circuit24B is input as the capture signal to the register 32. According to thecapture signal, the CPU 33 reads the data from the register 32.Therefore, when abnormality is detected in any of the monitoring placesand thus the output voltage from the output terminal Out of thecomparison circuit 24B becomes “L” level, the CPU 33 reads the data, forexample, from the register 32. In this way, internal temperatures in aplurality of places at the time of abnormality detection in theelectronic apparatus are recorded, which is useful for an analysis ofoperation in an abnormal state.

Although not shown, a configuration may be possible in which as analternative to the output signal from the output terminal Out of thecomparison circuit 24B, the control signal Vg3 to the third NMOStransistor 237 is used as the capture signal of the register 32. In thisconfiguration, also for the detection voltages in the other monitoringplaces, detection data is captured in the register 32 a and the likeusing the control signals Vg1, Vg2, and Vg4, and then read in the CPU33. In such a configuration, the detection data in the monitoring placesin the electronic apparatus is continuously read in the CPU 33.Therefore, for example, recording the maximum value of the detectiondata in the CPU 33 while updating makes it possible to analyze anoperational environment of the electronic apparatus 3 regardless ofwhether abnormality is detected or not. Especially as to a mobileapparatus, even if a level which is regarded as a high temperature isnot reached, there may be a case where occurrence of an abnormal statenotified by a user using the mobile apparatus for many hours is requiredto be dealt with. In such a case, if the highest temperature in eachplace in the electronic apparatus is recorded, the recorded temperaturecan be used for an analysis.

Moreover, capturing operation of the capture signals of the register 32and the other registers may be performed by the CPU 33 according toneed. In this case, it is clear that electric power consumption can bereduced compared to the case of continuous data capturing by using theabove-mentioned control signals Vg1 through Vg4 as the capture signal ofthe detection data.

As described above, according to Embodiment 5, since the detectionsignals which are respectively synchronous with the control signals Vg1through Vg4 obtained by dividing the clock signal Vck are generated, theprotection device also has a feature that the detection value is easilysubjected to analog-digital conversion and then processed. Therefore, adefect place of the electronic apparatus where abnormality occurs can bechecked without breaking the electronic apparatus 3.

It is to be note that the improper detection can be prevented byconfiguring the protection device as Embodiment 3 where the protectionoperation is performed when abnormality is repeatedly detected for apredetermined number of times.

Variation 1 of Embodiment 5

FIG. 7 shows a circuit configuration of a protection device according toVariation 1 of Embodiment 5. As shown in FIG. 7, the protection deviceaccording to Variation 1 has such a configuration that an AD converter31 b and a register 32 b are provided in an integrated circuit 101Cincluding main components of the protection device. In the presentvariation, the AD converters 31 and 31 a of FIG. 6 are represented by anAD converter 31A, and the registers 32 and 32 a are represented by aregister 32A.

In the present variation, the CPU 33 connected to the protection deviceallows operation of the AD converter 31A at arbitrary timing or at astop of operation of the electronic apparatus due to occurrence ofabnormality, and captures detection data recorded in the register 32A.The detection data captured in the CPU 33 is captured in a personalcomputer (PC) 35 via an interface device 34 such as a connector and thenanalyzed.

In this way, it is possible to downsize the protection device byintegrating a plurality of AD converters and a plurality of registers inthe protection device itself. Moreover, the integration of a register inwhich an occurrence history of the detected abnormal state can be storedaccording to a command from an external PC makes it possible to enhancea recording function.

Variation 2 of Embodiment 5

FIG. 8 shows Variation 2 of Embodiment 5 of the present inventionillustrating a mounting example of a protection device on an electronicapparatus. As shown in FIG. 8, in Variation 2, a first IC chip 121, asecond IC chip 122, and a protection device 101D are mounted on a firstmounting substrate 301. The first IC chip 121 and the second IC chip 122constitute the electronic apparatus 3 a. In the protection device 101D,main components of the present invention are integrated. On a secondmounting substrate 302, a third IC chip 123 and a fourth IC chip 124which constitute the electronic apparatus 3 b are mounted. On a thirdmounting substrate 303, a fifth IC chip 125 which constitutes anelectronic apparatus 3 c is mounted.

The first mounting substrate 301 and the second mounting substrate 302are supplied with a power source voltage by a first battery 10A. Thethird mounting substrate 303 is supplied with a power source voltage bya second battery 10B. Moreover, on the first mounting substrate 301, athird battery 10C is arranged as a back-up power source for thedetection data held in a protection device 101D.

Embodiments and Variations thereof described above refer to theconfiguration in which the battery 10 serves as an input power source ofthe protection device according to the present invention. In the presentvariation, not only temperature detection of the first battery 10Aitself which serves as a power source for the integrated protectiondevice 101D, but also temperature detection of the second battery 10Bwhich is independent of the protection device 101D are possible.

As shown in FIG. 8, as an example, a first thermistor 231 fortemperature detection is directly arranged on an upper surface of thefirst IC chip 121 mounted on the first mounting substrate 301. A secondthermistor 232 is arranged near one side surface of the third IC chip123 mounted on the second mounting substrate 302. A third thermistor 233and a fourth thermistor 234 are respectively arranged near side surfacesof the second IC chip 122 mounted on the first mounting substrate 301,the side surfaces facing each other. Moreover, for example, a fifththermistor 234 a is arranged on a side surface of the first battery 10A,and a sixth thermistor 234 b is arranged on a side surface of the secondbattery 10B.

The first thermistor 231 directly arranged on the upper surface of thefirst IC chip 121 can directly measure a temperature of a chip beingmonitored, but requires a connection by wiring 102A such as a wire.Compared to this, for example, in the case of the second thermistor 232arranged near the side surface of the third IC chip 123, a connectionby, for example, a wiring pattern 102B formed on the second mountingsubstrate 302 is possible.

As described above, according to Variation 2, a plurality of thermistors233 and 234 are provided for the second IC chip 122 being monitored. Inthis case, monitoring under a plurality of detection conditions such asa case where one of the two thermistors 233 and 234 detects abnormalityand a case where both of the thermistors 233 and 234 detect theabnormality is possible. As a result, determination of an occurrencestate of abnormality is facilitated. Moreover, Variation 2 is effectivealso in the case where the chip being monitored has a big size and thusa heat generation place can not be specified in one place.

Moreover, in Variation 2, the third battery 10C for backup is provided.Therefore, even if supply of electric power from the first battery 10Ais shut off due to abnormality, the detection data detected by theprotection device 101D can be held.

Embodiment 6

Embodiment 6 according to the present invention will be described belowwith reference to the drawings.

FIG. 9 shows a circuit configuration of a protection device according toEmbodiment 6 of the present invention. In FIG. 9, the same components asthose of the protection device of Embodiment 2 of FIG. 2 are given thesame reference numerals and descriptions thereof are omitted.

The protection device according to Embodiment 6 shown in FIG. 9 is anexample where the present invention is applied to a configuration of anelectronic apparatus in which the battery 10 is charged with electricpower from an AC adapter, an in-vehicle adapter, or the like via acharging apparatus 5.

As shown in FIG. 9, in a configuration in which the battery 10 can becharged, a voltage output from an external power source 4 is supplied tothe charging apparatus 5 via a third PMOS transistor 21 a. A secondcontrol circuit 22 a applies a signal V2 to the gate of the third PMOStransistor 21 a to control a current from the external power source 4. Afourth PMOS transistor 25 a is connected between the gate and the sourceof the third PMOS transistor 21 a.

Differences from Embodiment 2 are that the second thermistor 232 isinstalled on or arranged near the charging apparatus 5 to detect atemperature of the charging apparatus, and that the fourth PMOStransistor 25 a connected between the gate and the source of the thirdPMOS transistor 21 a is turned ON or OFF along with the second PMOStransistor 25 by the comparison circuit 24.

With this configuration, when temperature detection performed inmonitoring places including the charging apparatus 5 results indetection of an abnormal temperature in any one of the monitoringplaces, the supply current from the battery 10 to the electronicapparatus 3 is shut off and the fourth PMOS transistor 25 a is turnedON, causing the third PMOS transistor 21 a to transition to the OFFstate, which simultaneously shuts off a supply current from the externalpower source 4 to the charging apparatus 5.

That is, in Embodiment 6, a place where the power source is shut off isnot limited to a single power source supply path. Providing a pluralityof shut-off switching circuits makes a protection function effectivealso for an electronic apparatus including a plurality of power sources.

Embodiment 7

Embodiment 7 of the present invention will be described below withreference to the drawings.

FIG. 10 shows a block configuration of a protection device according toEmbodiment 7 of the present invention. As shown in FIG. 10, theprotection device according to Embodiment 7 includes an integratedcircuit 400 and five thermistors 410 for, for example, temperaturedetection, wherein main components are integrated in the integratedcircuit 400.

The integrated circuit 400 is connected to an external power source 420such as an AC adapter, a battery 430, a charging apparatus 440 forcharging the battery 430 with a current output from the external powersource 420, a first switch 450 which is provided between the externalpower source 420 and the charging apparatus 440 and which is, forexample, an NMOS transistor, a second switch 460 which is providedbetween the charging apparatus 440 and the battery 430 and which is anNMOS transistor, and a resistor 470 which is provided between thebattery 430 and the second switch 460.

The integrated circuit 400 is further connected to an external device480 which includes an AD converter 481 for performing analog-digitalconversion of detection data of, for example, a current and atemperature detected by the integrated circuit 400, and a CPU 482 inwhich the detection data digitalized by the AD converter 481 is recordedand processed.

The integrated circuit 400 includes a voltage detection protectioncircuit 401, a current detection protection circuit 402, a temperaturedetection protection circuit 403, a protection control circuit 404, andan analog output circuit 405.

The voltage detection protection circuit 401 detects an output voltageof the external power source 420. When the voltage detection protectioncircuit 401 detects an overvoltage, the voltage detection protectioncircuit 401 turns off the first switch 450.

The current detection protection circuit 402 detects a charging currentor a discharging current of the battery 430 from a voltage drop acrossthe resistor 470. When the current detection protection circuit 402detects an overcurrent, the current detection protection circuit 402turns off the second switch 460.

The temperature detection protection circuit 403 feeds a predeterminedcurrent to each thermistor 410 and detects an ambient temperature ofeach thermistor 410 from the amount of a voltage drop across thethermistor. When the temperature detection protection circuit 403detects an overheating state, the temperature detection protectioncircuit 403 turns off the second switch 460.

The protection control circuit 404 controls the voltage detectionprotection circuit 401, the current detection protection circuit 402,and the temperature detection protection circuit 403.

The analog output circuit 405 outputs detection data detected by thecurrent detection protection circuit 402 and the temperature detectionprotection circuit 403.

In FIG. 10, the protection control circuit 404 included in theprotection device realizes a method for detecting a quantity ofelectricity according to the present invention. Specifically, protectioncontrol circuit 404 includes a clock generator for generating a clocksignal having a 10-μs pulse in a cycle of 1 ms, for example, and dividesthe generated clock signal to sequentially drive the detection circuits402 and the 403. In Embodiment 7, a current detection place is oneplace, that is, the resistor 470 and temperature detection places arefive places, that is, the thermistors 410. Therefore, since each of thedetection places operates during a 10-μs detection period in a cycle of6 ms, its electric power consumption is greatly reduced compared to thecase of continuous detection.

Detection data detected by the current detection protection circuit 402and the temperature detection protection circuit 403 is output from theintegrated circuit 400 included in the protection device to the externaldevice 480 by the analog output circuit 550. The detection data capturedin the external device 480 is recorded as digital data and subjected toan appropriate process.

It is to be noted that also in Embodiment 7, an AD converter, a resist,or the like may be integrated in the integrated circuit 400 included inthe protection device as Variation 1 of Embodiment 5 of FIG. 7.

FIG. 11A shows an example of a graph drawn based on current detectiondata which is output from the current detection protection circuit 402of the protection device and recorded in the external device 480. FormFIG. 11A, it is possible to see a history as follows. The currentdetection protection circuit 402 detected an overcurrent exceeding anupper limit (threshold value) at a time t5, and thus turned off thesecond switch 460. Therefore, the current value once decreased to 0, andthen the current increased due to reactivation. At a time t10, thecurrent detection protection circuit 402 detected an overcurrent again,and thus turned off the second switch 460.

Likewise, FIG. 11B shows an example of a graph drawn based ontemperature detection data output from the temperature detectionprotection circuit 403 of the protection device and recorded in theexternal device 480. The temperature detection protection circuit 403detects a temperature in each monitoring place according to, forexample, a voltage value which generates a resistance value of eachthermistor 410 when a current is fed for 10 μs in a cycle of 6 ms. FromFIG. 11B, it is possible to see a history as follows. The temperaturedetection protection circuit 403 detected a temperature exceeding anupper limit (threshold value) at a time t25, and thus turned off thesecond switch 460. Therefore, the temperature of the monitoring placewhere electric power supply was shut off lowered, and then thetemperature increased due to reactivation. At a time t30, thetemperature detection protection circuit 403 detected an overheatingstate again, and thus turned off the second switch 460.

As described above, when the integrated circuit 400 included in theprotection device according to Embodiment 7 is adopted, the protectionfunction for the electronic apparatus can be realized with low electricpower consumption. Moreover, since an operational history can berecorded, breakdown analysis and the like can be certainly performedwithout breaking the electronic apparatus.

In the protection device in each Embodiment of the present invention,the operation of shutting off power source supply on abnormalitydetection has been described as protection operation. However, after theshutoff stops operation of the electronic device and lowers thetemperature or the like allowing the electronic device to get out of theabnormal state, the protection device is generally required to maintainthe shutoff of the power source supply. This is not a feature of thepresent invention, and thus descriptions thereof are not given. However,such a configuration in which the protection device is fed with electricpower directly from a battery or an external power source device and alatched circuit is provided to maintain the protection operation isself-evident.

INDUSTRIAL APPLICABILITY

In a protection device and a method for driving the same according tothe present invention, detection operation is performed insynchronization with a clock signal, so that electric power consumptionrequired for detecting abnormality can be reduced. Therefore, theprotection device and the method for driving the same according to thepresent invention are applicable to, for example, a protection devicefor detecting an abnormal temperature, an abnormal current, and the likeof an electronic apparatus to protect the electronic apparatus, and areapplicable specifically to a protection device for a mobile phone and anin-vehicle apparatus which are used for many hours.

1. A protection device for detecting a temperature, a voltage, or acurrent in a predetermined monitoring place in an electronic apparatussupplied with electric power from an external power source to protectthe electronic apparatus from an excessive temperature, an overvoltage,or an overcurrent, the protection device comprising: a detection elementarranged in the monitoring place for detecting the temperature, thevoltage, or the current of the electronic apparatus to output anelectric signal; an oscillating circuit for generating a clock signalhaving a predetermined cycle and a predetermined ON time; and adetection circuit for detecting the electric signal during the ON timeof the clock signal, the electric signal being generated in thedetection element, wherein supply of the electric power to theelectronic apparatus is shut off according to an output signal outputfrom the detection circuit.
 2. The protection device of claim 1, furthercomprising a switching circuit for controlling the supply of theelectric power to the electronic apparatus, the switching circuit beingprovided for an electric power supply line between the external powersource and the electronic apparatus, wherein the detection element is atemperature detection element for detecting a temperature of theswitching circuit to output the electric signal according to thedetected temperature, and the switching circuit is turned off accordingto the output signal of the detection circuit.
 3. The protection deviceof claim 1, further comprising a switching circuit for controlling thesupply of the electric power to the electronic apparatus, the switchingcircuit being provided for an electric power supply line between theexternal power source and the electronic apparatus, wherein thedetection element is a temperature detection element for detecting atemperature of an element constituting the electronic apparatus tooutput the electric signal according to the detected temperature, andthe switching circuit is turned off according to the output signal ofthe detection circuit.
 4. The protection device of claim 1, furthercomprising a switching circuit for controlling the supply of theelectric power to the electronic apparatus, the switching circuit beingprovided for an electric power supply line between the external powersource and the electronic apparatus, wherein the detection element is avoltage detection element which is connected to the electric powersupply line for detecting a voltage of the electric power supply line tooutput the electric signal according to the detected voltage, and theswitching circuit is turned off according to the output signal of thedetection circuit.
 5. The protection device of claim 1, furthercomprising a switching circuit for controlling the supply of theelectric power to the electronic apparatus, the switching circuit beingprovided for an electric power supply line between the external powersource and the electronic apparatus, wherein the detection element is acurrent detection element which is connected to the electric powersupply line for detecting a current responsive to an output current ofthe external power source to output the electric signal according to thedetected current, and the switching circuit is turned off according tothe output signal of the detection circuit.
 6. The protection device ofclaim 1, further comprising a protection control circuit for generatingthe electric signal during the ON time of the clock signal, the electricsignal being input to the detection element, wherein the detectionelement includes detection elements arranged in N (N is an integergreater than or equal to 2) detection places, and the protection controlcircuit drives the detection elements according to N different phasessynchronous with the clock signal.
 7. The protection device of claim 6,wherein the protection control circuit includes a divider circuit fordividing the clock signal by at least N.
 8. The protection device ofclaim 1, further comprising a judging circuit which includes acomparison circuit for comparing the output signal of the detectioncircuit with a reference signal serving as a reference and outputting aresult of the comparison, wherein the judging circuit counts an outputsignal of the comparison circuit, and when a result of the count exceedsa predetermined number of times, the judging circuit shuts off thesupply of the electric power to the electronic apparatus.
 9. Theprotection device of claim 8, wherein the judging circuit furtherincludes: a delay circuit for outputting a signal obtained by delayingthe clock signal for a predetermined time; the detection circuit forintermittently supplying a current to the detection element according tothe clock signal to output the signal generated in the detectionelement; a logical circuit for performing logical AND operation of theoutput signal of the comparison circuit and the signal output from thedelay circuit; and a counter circuit whose reset terminal receives anoutput signal of the logical circuit and whose clock input terminalreceives the output signal of the comparison circuit for countoperation, wherein the supply of the electric power to the electronicapparatus is shut off according to an output signal of the countercircuit.
 10. The protection device of claim 1, further comprisingrecording means for recording a current, a voltage, or a current atwhich the supply of the electric power to the electronic apparatus isshut off.
 11. The protection device of claim 10, wherein the recordingmeans records a bigger one of data detected by the detection circuit anddata in the recording means.
 12. The protection device of claim 10,further comprising a central processing unit, wherein the recordingmeans operates according to a signal given from the central processingunit.
 13. The protection device of claim 12, further comprisingtransmission means for externally transmitting an internal signal heldin the central processing unit.
 14. The protection device of claim 12,wherein the central processing unit is connected to a first power sourcewhich is detachably provided, and the recording means is connected to asecond power source which is provided independently of the first powersource.
 15. A protection device for detecting temperatures, voltages, orcurrents in predetermined monitoring places in a first electronicapparatus and a second electronic apparatus to protect the electronicapparatuses from an excessive temperature, an overvoltage, or anovercurrent, the protection device comprising: an oscillating circuitfor generating a clock signal having a predetermined cycle and apredetermined ON time; a detection circuit for detecting thetemperatures, the voltages, or the currents in the predeterminedmonitoring places during the ON time of the clock signal; and aswitching circuit for shutting off supply of electric power to theelectronic apparatuses according to an output signal of the detectioncircuit; wherein the oscillating circuit and the detection circuit areintegrated to constitute an integrated circuit, the integrated circuitand the first electronic apparatus are mounted on a first substrate, thesecond electronic apparatus is mounted on a second substrate, the firstsubstrate is supplied with the electric power from an external powersource for the first substrate, and the second substrate is suppliedwith the electric power from an external power source for the secondsubstrate, and at least one of the integrated circuit, the firstelectronic apparatus, the second electronic apparatus, the externalpower source for the first substrate, and the external power source forthe second substrate is one of the monitoring places.
 16. A protectionmethod using a protection device for detecting a temperature, a voltage,or a current in a predetermined monitoring place in an electronicapparatus to protect the electronic apparatus from an excessivetemperature, an overvoltage, or an overcurrent, the protection deviceincluding: a detection element arranged in the monitoring place fordetecting a value of the temperature, the voltage, or the current in themonitoring place; a clock generation circuit for generating a clocksignal which is output from the clock generation circuit, the clocksignal having a predetermined cycle and a predetermined ON time; and acurrent source for outputting a signal current during the ON time of theclock signal, the protection method comprising the steps of: collectinga quantity of electricity generated by applying the signal current tothe detection element; and protecting the electronic apparatus accordingto the collected quantity of the electricity.
 17. A method forprocessing a signal using a protection device for detecting atemperature, a voltage, or a current in a predetermined monitoring placein an electronic apparatus to protect the electronic apparatus from anexcessive temperature, an overvoltage, or an overcurrent, the methodcomprising the steps of: generating a clock signal having apredetermined cycle and a predetermined ON time; detecting thetemperature, the voltage, or the current in the monitoring place duringthe ON time of the clock signal; shutting off supply of electric powerto the electronic apparatus according to an output signal of a detectioncircuit; and recording output data from temperature detection means,voltage detection means, or current detection means at a time when thesupply of the electric power is shut off according to the output signalof the detection circuit.
 18. The method of claim 17, further comprisingthe step of transferring the output data to a central processing unitprovided outside.
 19. A method for detecting a quantity of electricityusing a protection device for detecting a temperature, a voltage, or acurrent in a predetermined monitoring place in an electronic apparatusto protect the electronic apparatus from an excessive temperature, anovervoltage, or an overcurrent, the protection device including: adetection element arranged in the monitoring place for detecting a valueof the temperature, the voltage, or the current in the monitoring place;a clock generation circuit for generating a clock signal which is outputfrom the clock generation circuit, the clock signal having apredetermined cycle and a predetermined ON time; and a current sourcefor outputting a signal current during the ON time of the clock signal,the method comprising the steps of: (a) applying the signal current tothe detection element; and (b) detecting the quantity of the electricitygenerated from the detection element due to the application of thesignal current.
 20. The method of claim 19, wherein the monitoring placeincludes a plurality of monitoring places provided in the electronicapparatus, the detection element includes a plurality of detectionelements respectively arranged in the plurality of monitoring places,step (a) includes sequentially applying the signal current from thecurrent source to the plurality of the detection elements; and step (b)includes sequentially detecting the quantity of the electricitygenerated from each of the detection elements due to the sequentialapplication of the signal current.